In a food processor, pulse the quartered onion until finely chopped.
Add the nuts and oats (or cooked rice) to the processor. Pulse a few times until the nuts are chopped into a coarse meal. Be careful not to over-process into a paste.
Add your chosen binder (ketchup, miso, etc.) , spice mix, salt, pepper, and the egg. Pulse just until the mixture comes together. If it seems too dry, add a splash of water or stock. The mixture should be moist but hold its shape.
Let the mixture rest for 5-10 minutes. This helps the oats absorb moisture and makes the patties easier to form.
Shape the mixture into 4 to 6 evenly-sized patties, about 1/2-inch thick.
Heat the oil in a large nonstick or cast-iron skillet over medium heat.
Carefully place the patties in the hot skillet.
Cook for about 5 minutes on the first side, until golden brown and crisp.
Flip the burgers, reduce the heat slightly, and cook for another 3-4 minutes, or until firm and cooked through.
Serve immediately on buns with your favorite toppings, or let them cool completely before storing.
Shape the patties and freeze them raw on a baking sheet before transferring to a freezer bag.
Cook directly from frozen, adding a few extra minutes of cooking time per side.
